Water splitting: Plants provide blueprint for cheap hydrogen production

Apr 15, 2013 by Ross Barker

Schematic of the ECPB-based approach to water splitting. Credit: Nature Chemistry

(Phys.org) —The process by which plants convert energy from the sun's rays into chemical 'fuel' has inspired a new way of generating clean, cheap, renewable hydrogen power which could solve looming problems with the UK's energy infrastructure.

Hydrogen is a significant source of energy which can be burned to produce power with no negative impact on the environment, unlike power produced by burning fossil fuels. Hydrogen gas can be easily produced by splitting water into its constituent elements – hydrogen and oxygen.

Plants' powers of photosynthesis allow them to harness the energy of the sun to split water molecules into hydrogen and oxygen at separate times and at separate physical locations in the plant's structure.

By applying direct current to water via a positive and a negatively-charged electrode in a process known as electrolysis, scientists have long been able to break the bonds between hydrogen and oxygen, releasing them as gas.

Industrial processes to produce pure hydrogen from water require expensive equipment and rigorous oversight to ensure that the gases do not mix. Accidental mixing of the gases can lead to accelerated decay of materials involved in the process or even dangerously explosive mixtures.

In a new paper in the journal Nature Chemistry published today (Monday 14 April), Professor Lee Cronin and Dr Mark Symes of the University of Glasgow outline how they have managed to replicate for the first time plants' ability to decouple the production of hydrogen and oxygen from water using what they call an electron-coupled proton buffer (ECPB).

Dr Symes: "What we have developed is a system for producing hydrogen on an industrial scale much more cheaply and safely than is currently possible. Currently much of the industrial production of hydrogen relies on reformation of fossil fuels, but if the electricity is provided via solar, wind or wave sources we can create an almost totally clean source of power.

"The ECPB is made from commercially-available phosphomolyb-dic acid. The properties of this material allow us to collect and store the protons and electrons which are generated when we oxidise water, to give oxygen as the only gaseous product. We can then use those stored protons and electrons to produce only hydrogen at a time of our choosing, allowing us to produce pure hydrogen gas on demand with none of the difficulties of the current electrolytic process where the two are unavoidably produced at the same time.

"Using a single precious metal electrode and an ECPB to generate hydrogen and oxygen from water would allow much more economically-viable large-scale generation of hydrogen than is currently possible."

Professor Cronin added: "One of the problems of generating electricity via renewable power is that the output either needs to be used immediately or stored. Using renewable power to produce hydrogen allows us to capture the electricity in a state which is easily stored and distributed and, when burned, creates no problems for the environment.

"In the next couple of decades we're likely to face significant problems because the infrastructure which allows the distribution of electricity across the country via power lines is ageing badly and will become increasingly less fit for purpose. There are currently no solid plans in place to source the billions of pounds it will cost to overhaul the system.

"However, the existing gas infrastructure which brings gas to homes across the country could just as easily carry hydrogen as it currently does methane. If we were to use renewable power to generate hydrogen using the cheaper, more efficient decoupled process we've created, the country could switch to hydrogen to generate our electrical power at home. It would also allow us to significantly reduce the country's carbon footprint."

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So they are able to isolate hydrogen from water and at the same time store it. Then later it can be released to be used. But what is the efficiency of this process? If we assume transmission of electricity to be say 90%, I bet that is hard to beat.

"However, the existing gas infrastructure which brings gas to homes across the country could just as easily carry hydrogen as it currently does methane."

What a bunch of BS. Hydrogen molecules are much smaller than methane and would leak out of a methane distribution system at an alarming rate. That is one of the problems with hydrogen, we cannot build a container that is capable of storing it without leakage.

No question, our clean and bright future lay on the most basic element of This Universe. As we Humans are also part of MotherNature which will eventually found the simpliest form to transform subtance to energy. High Five for University of Glasgow!

No question, our clean and bright future lay on the most basic element of This Universe. As we Humans are also part of MotherNature which will eventually found the simpliest form to transform subtance to energy. High Five for University of Glasgow!

You are aware that you get all the water back after use - and even more pure than before?

So let me get this straight, most of the solar farms and many of the wind farms would have to draw water from the aquifers in order to produce hydrogen. This hydrogen would then power automobiles and supply gas to users municipalities. How exactly would this pure water be recovered?

When you react hydrogen in a fuel cell (or in a combust it in a combustion engine) you get H2O back.

And it gets back into the river it came fromt via canalisation and purification plants (as usual) or as water vapor and later as rain. It's not rocket science.

If the hydrogen is stored on site to produce power then the whole thing can be a closed loop. Same for large 'hydrogen buffer stations' that just draw power off the grid when excess is available and feed it back in when power is needed.

How exactly would this pure water be recovered?

For your car: If you don't catch it it drips out the back and seeps back into the ground - replenishing groundwater.

We hear about revolutionary hydrogen production method about once a month for the last 3 years or so on PhysOrg. Researchers and inventors, please, please, reining in your hypes and enthusiasm until you guys can give us more concrete, near-application products! Thank you all.

"When you react hydrogen in a fuel cell (or in a combust it in a combustion engine) you get H2O back."

My point was that most solar farms and some wind farms are located in arid areas where water is at a premium. Per the article, the hydrogen would be used in major metropolitan areas where there is natural gas infrastructure. Thus, you wind up moving vast amounts of water from a dry area to a wetter one. The water would have to be piped in from a major source of surface water.

Thus, you wind up moving vast amounts of water from a dry area to a wetter one.

Why? What stops you from producing the hydrogen in the city from power you draw off the grid during excess production periods?Load has to be balanced vs. production. If you produce more you can artificially up the load by making hydrogen somewhere (anywhere). It's also a perfect way of using the overproduction that s currently the norm because of net stability issues (and just gets shed), as hydrogen producers can be turned on and off in a snap.

Where you produce the power and where you produce the hydrogen is independent of each other.